A new report from the U.S. Department of Energy reevaluates the agency’s strategic plan for supporting clean energy technologies that can help decrease energy use and carbon emissions.

The Energy Department’s first Quadrennial Technology Review found that the agency was making too much of an effort to support and fund futuristic next-generation technologies and not enough of an effort to support and fund existing clean energy technologies that are already proven to work.

According to the report, the government needs to focus on technologies that can survive the time between a technology’s pilot status and when it becomes commercialized and available to the public. During this critical period of time, known as the “valley of death,” many projects tend to fail from a lack of funding.

The report highlighted transportation technologies, namely fuel efficiency technologies and electric vehicle technologies, as having a greater likelihood of clearing the commercialization hurdle than ambitious clean energy or building efficiency projects. Cars are a better target for change, according to the report, because cars spend an average of 15 years in active use and don’t last nearly as long as buildings.

According to the report, the government can change the way energy is used more quickly by focusing on cars because it’s the sector in which people are going to need new products more often and a sector which presents greater opportunities for more frequent adoption of new energy efficiency technologies.

Although the Energy Department proposes in the report to back off funding for clean energy technologies that “are multiple generations away from practical use,” it said that it won’t abandon groundbreaking research.

Recently the Energy Department announced more than $250 million in funding to research and develop next-generation solar power, hydropower, offshore wind energy, geothermal power and drop-in biofuel technologies.